Catalytic cracking of partially oxidized hydrocarbons



Dec. '11, 1945. y R. F, RUTHRUFF 2,390,556

CATALYTIC CRACKING 0F PARTIALLY OXIDIZED HYDROGARBONS MET/ALLY OXIDIZEDLIQUID HYDRO CHEB ONS INVE NTOR De@ 11 1945' R. F. RUTHRUFF 2,390,556

CATALYTIC CRACKING OF PARTIALLY OXIDIZED HYDROCARBONS Dea ll, 1945.

R. F. RUTHRUFF CATALYTIC CRAGKING OF PARTIALLY OXIDIZED HYDROCARBONSFiled July 7, 1941 JRST 4 Sheets-Sheet 4 GSOLINE GIS TH IPD CA THLYTZ C/K /N G Z ONE GSOL INE CYCLE WTE?? sTocK PART/AL O/Y/.DHT/ON ZONE h/H TEETHIRD L OXID/z 270A/ ZONE INVENTOR I Patented Dec. 11, 1945 CATALYTICCRACKING F PARTIALIIY `OXIDIZED HYDROCARBONS Robert F. Ruthruff,Chicago, Ill.

Application July 7, 1?41, Serial No. 401,329

34 Claims.

This invention relates to improved processes for catalytic cracking.lMore particularly, this invention relates to improved processes for thecatalytic cracking of charging stocks comprising or consisting ofpartially oxidized liquid hydrol carbons.

Ihe thermal conversion of hydrocarbons of higher boiling point intohydrocarbons of lower boiling point and more particularly intohydrocarbons in the motor fuel boiling range is well known in the art.Such thermal conversion processes suffer from many disadvantages; amongthese may be mentioned the comparatively low octane rating of the motorfuel produced and the high production of undesirable products, such asgas and tar, having little commercial value. These and otherdisadvantages have led to the development of various catalytic processesfor the conversion of hydrocarbons of higher boiling range intohydrocarbons of lower boiling range `and more particularly intohydrocarbons in the motor fuel boiling range.A In comparison withthermal processes, the motor fuel produced by the catalytic conversionof higher boiling hydrocarbons is of much higher octane rating, the gasproduction is appreciably lower, and the production of material with ahigher carbon to hydrogen ratio than that of the higherlooilinghydrocarbon charge is much decreased.

Contact agents for the catalytic cracking of hydrocarbons of higherboiling point to form hydrocarbons of lower boiling point, particularlyhydrocrabons within the usual motor fuel boiling range, may be dividedinto three broad classes as follows:

I. Natural or acid treated materials of an argillaceous nature,particularly those of the montmorillomtic or bentonitic type.

II. Synthetic silica-alumina complexes.

III. Natural orA synthetic silica-magnesia complexes.

Contact materials falling in class I are relatively cheap butunfortunately they exhibit a more or less rapid decline in activityduring continued use which involves alternating periods wherein suchcontact agents are employed in the conversion reaction and in .beingregenerated.

Such materials are rather sensitive toand are` deteriorated by steam,particularly at elevated temperatures. These contact agents are onlymoderately active which is not necessarily disadvantageous. For example,in `catalytic cracking, it is highly desirable to operate in the vaporphase and obviously, to achieve such a condition when charging ahydrocarbon fraction of very highboiling point such as reduced crude,heavy virgin gas oil, heavy viscosity breaker gas oil, heavy coker gasoil and the like, a very high temperature is required.l When highly'active contact agents are employed at these elevated temperatures,overcracking of the charge occurs resulting in undesirable secondarydecomposition reactions. However, when an only moderately activecatalyst is employed, such as a member of class I, high temperatures maybe employed without encountering secondary decomposition reactions o-rovercracking.

Contact materials falling in class II are relatively expensive butexhibit practically constant activity with long continued use. TheseContact agents are very sensitive to steam and are rapidly deterioratedthereby, particularly at elevated temperatures. These contact agents arehighly active.

Contact materials falling in class III range from cheap naturalmaterialsto relatively expensive synthetic products.` The activity ofthese materials remains constant with long continued use. They arepractically unaffected by steam and are only moderately active which, ashas been previously shown, is not necessarily disadvantageous.

As is known to those skilled in the art, the major disadvantage ofcatalytic cracking processes resides in the highly refractory cyclestocks produced. In the catalytic cracking of a hydrocarbon charge, theless refractory components thereof are preferentially attacked and theresulting cycle stock, even though of the same boiling range or even ofslightly lower average boiling point than that of the charge, isscarcely affected if again passed over the catalyst. In once throughcatalytic cracking it is di'flicult, as a rule, to obtain much more than40% gasoline. This leaves a large amount of refractory cycle stock whichwill give a little additional gasoline on repassage over the catalystbut the yield is so low that recycling to completion, as is commonlydone in thermal cracking processes, is impossible or highly undesirable.

Many attempts have been made to obviate the disadvantages arisingthrough the highly refractory nature of the cycle stocks obtained incata' lytic cracking operations.

For example, it has been suggested that cycle stocks obtained duringonce through catalytic cracking be cracked thermally, recycling tocompletion. Obviously, this method of operation means a return in partto thermal cracking with all the disadvantages thereof. Certainoperating schemes have been employed in catalytic cracking to accomplishthe highly active catalyst at high temperature.

same result. example, the cycle stock obtained in once through catalyticcracking, either at low temperature with a-highly active catalyst or athigher temperature with a moderately active catalyst (dependingprimarily on the boiling range of the charge) is again catalyticallycracked once through in a second zone using a Another such schemeinvolves the once through catalytic cracking of a comparatively lowboiling charging stock at low temperature with a highly activecatalyst., admixing the resulting cycle stock with a comparatively highboiling charging stock and processing the mixture at-high teinperaturewith a moderately activecatalyst. A more complicated but betterarrangement involves catalytically cracking a comparatively low boilingcharging stock at low temperature with a highly active catalyst,separately catalytically cracking a comparatively high boiling chargingstock at high temperature with a moderately active catalyst, admixingthe cycle'stocks from -the two catalytic cracking zones andcatalytically cracking the resulting blend in a third zone at hightemperature with a` highly active catalyst. These, and other similarschemes, while more or less useful, are obviously not perfect since inall of them recycling to completion is impossible or highly undesirable.

It has also been suggested to solvent extract refractory cycle stocksfrom catalytic cracking, discarding the extract and recycling therafnate to the' catalytic cracking zone. Obviously, this scheme does notprovide for the complete utilization of cycle stock. In my copendingapplicaltion, S. N. 334,741, filed 'May 13, 1940, noW U. S.

Patent 2,312,445, issued March 2, 1943, a process is disclosed whereincycle stock from catalytic cracking is catalytically hydrogenated, theresulting liquid product being recycled to the catalytic cracking zone.While by this process complete utilization of cycle stock is achieved,the apparatus required is rather complicated and quite expensive. Also asource of hydrogen must be provided.

I have found that by partially oxidizing refractory cycle stock fromcatalytic cracking operations or from other sources, the resultingVpartially oxidized liquid hydrocarbons become quite amenable tocatalytic cracking. Such partially oxidizedliquid hydrocarbons may becatalytically cracked in the presence of contact agents selected fromany of the three classes previously mentioned. However, with catalystsfrom class I, the usual more or less rapid permanent decline in activitywith continued use is observed, sometimes in an enhanced degree incomparison with the same catalysts when employed in processingnon-oxidized stocks.` With respect to catalysts from class II, a fairlyrapid and permanent decline in activity is observed when these areemployed in the catalytic cracking of partially oxidized liquidhydrocarbons. On the other hand, the catalysts of class III have beenfound to be eminently suitable for use as contact agents in thecatalytic cracking of partially oxidized liquid hydrocarbons, exhibitinga satisfactory activity, especially at high temperatures, which remains'constant or practically so with long continued operations.

I attribute the excellence of class III contact agents, when used ascatalysts in the catalytic accanito f oi' partially oxidized iiquidhydrocarbons, it is evident that steam is formed which presumablypermanently destroys the activity of class I and II contact agents withmore or less rapidity but which has no eiIect on the, contact agents ofclass III. While this explanation is believed to be correct, it is to beunderstood that it represents theory only and the scope of the instantinvention is in no way to be limited thereby.

. catalysts and their preparation are cracking of partially oxidizedliquid hydrocarbons, to the fact that these materials are insensitive tosteam. During the catalytic cracking.

Many silica-magnesia complexes are suitable for the purposesvof thisinvention and many methods are available for the preparation thereof.Selected illustrative examples of such presented below in Examples 1. to23.

One. method for the preparation of silica-magnesia complexes suitablefor the purposes of the instant invention involves double decompositionas exemplified by a process wherein a suitable soluble silicate, e. g.sodium silicate, is allowed to reactwith a soluble magnesium compound,e. g. magnesium sulfate or magnesium chloride; Preferably a solution ofthe soluble silicate is A addedslowly, with agitation, to a'solution ofthe soluble magnesiumfcompound. If the addition is too rapid or if thereaction mixture is not agitated, local spots of high alkalinity developwhich result in the production of. zeolitic type precipitates from whichit is diilicult or impossible to remove alkali metal compounds bywashing. These zeolitic type materialsare not as suitable for thepurposes of the instant invention as are silica-magnesia complexes freefrom alkali metal compounds. For the same reason, it is inadvisable toadd the solution of the magnesiumr salt to the soluble silicate solutionsince by this procedure it is almost impossible to avoid formation ofzeolitic type compounds.

If desired, the silica-magnesia ratios of the complexes formed may bevaried over wide limits by use of alkali metal silicates of varyingalkali metal oxide-silica ratios. This is illustrated in Examples 1 to 3below.- A similar result may be accomplished by keeping the alkali metaloxide-silica ratio constant and using a solution of a magnesium saltcontaining more or i less acid so that the anion of the magnesium saltplus the anion of the acid is stoichiometrically equivalent to or inslight excess over .the alkali metal oxide of the soluble silicate.

Example 1 To 25 liters of a solution containing a total tainedY 38.5\%magnesia and 61.5% silica onthe water free basis.

1 Example 2 To 25 liters of a solution containing a total of,

800 g. of MgSor'lHiO there were added over a period of four hours, withstirring, 2.81 liters of a solution containing 466 g. NaiO-1.5SiOz. Theresulting precipitate was separated by filtrationand was washed bymaking into a slurry with water and ltering, this washing operationbeing repeated several times. tained 29.5% magnesia and 70.5% silica onth Water free basis. y f

The nal product con-k.

'washing with aoidulated water.

processing.

' `Eauzmple 3 To 25 liters of a solution containing a total of 800 s.MgSO4-7Hz0 there were added over a period of four hours, with stirring,6.18 liters of a solution containing 797 g. NaiO3.25SiOz. The resultingprecipitate was separated by i'lltration and was washed by making intoa' slurry with water and filtering, this washing operation beingrepeated several times. 'I'he iinal product contained 15.5% magnesia and84.5% silica on the water free basis.

. In preparations made in accord with the above examples one can washinitially with slightly acidulated water followed by several washingswith pure water. If this procedure is used, then it is not so necessaryto fix the anion of the magnesium* salt (or the anion of the magnesiumsalt plus the vanion of an `acid added thereto) stoiohiometricallyrequal to or greater thanthat of the alkali metal oxide' of the solublesilicate. Any` alkaline complex vformed under such conditions will beconverted over to the acid form by Even so, silicamagnesia complexesformed in this way are rarely equal in activity to those originallyprecipitated in tLe acid form. Also, this method oi' washing is very aptto give trouble because of the precipitate peptizing. Occasionally, evenin the ordinary washing method, Deptizing occurs. Whenever theprecipitate shows a tendency to peptize lt may be coagulated bywashingwith a dilute solution of a non-reactive electrolyte, preferably oneeasily removable in subsequent operations such as, for example, ammoniumchloi ride or ammonium nitrate. As will be obvious to those skilled inthe catalytic art, when washing the precipitate suitable tests areapplied to the filtrate from time to time so as to follow the removal ofundesired components.

Preoipitates formed in accordance with Examples 1 to 3 may be dried toform a powder which may then be formed into pellets as usual, employinga binder such as Vololay bentonite, if desired. Or, the dry powder maybe mixed with wet precipitate and the moist mixture extruded (with abinder if desired) to form spaghetti which is out to length and dried.Alternatively, the washed but undried precipitate may be suspended inwater to give about 7.5% solids and treated with a small amount of apreferably volatile acid, such as carbonio, acetic or hydrochloric, topeptize the precipitate. The resulting thixotropic gel is then cast intopans and slowly dried to formhard particles of appreciable size.

A somewhat different scheme of preparation is used in Example 4. Herethe sodium silicate solution is made definitely acid and a magnesiumsalt solution is added to the resulting rather stable sol. The mixtureis then precipitated with an excess of ammonia. Ammonia does not haveany deleterious effect on catalyst activity, presumably because it isnot a xed alkali and hence is completely removed during subsequentExample 4 One liter of a solution containing 34.3% by weight of`Na2O3.5SiO2 was diluted with 6 volumes of water. The thus diluted waterglass solution was vigorouslyv stirred and 600 cc. ooncentrated (d:1.19) hydrochloric acid were added rapidly. To the resulting silica.sol was added 2000 g. MgClz-6H2O in 1500 cc. water, following which 1000cc.` concentrated ammonia solution (d.=0.88) were added `slowly withstirring. After assauts standing over night. the resulting precipitatewas separated by filtration and was washed by being vmade into a slurrywith water and filtering, this washing operation being repeated severaltimes. The final product contained 31% magnesia and 69% silica on thewater vfree basis.

By -a modification of the process of Example 4 no ammonia is required.In this modification the sodium silicate solution is, treated with butlittle more, say 5% excess, acid than is stoichiometrically equivalentto the sodium oxide of the silicate. A magnesium salt solution isy addedand the desired complex precipitates, a process that may be acceleratedto completion by boiling.

By a slight change in the modification described in the previousparagragh, a somewhat more satisfactory catalyst is obtained. The sodiumsilicate solution is pmade but slightly acid as before and then is agedprior to treatment with the solution of the magnesium compound. The timeof aging depends upon the exact acidity of the slightly acid ,sodiumsilicate solution. If the pH lis 6, the acidled sodium silicate solutionis aged 30 minutes or more, if the pH is 5, the acidified sodiumsilicate solution is aged 2.5 hours or more.

Example 5 Catalysts made in accordance with the teachings of mycopending application, S. N. $113,898, filed January 15, 1940, now U. S.Patent 2,323,728, issued July 6, 1943, especially Examples 21B, 2B and3B.

` Example 6 Eample 7 One mole of silicon tetrachloride was diluted withan equal volume of absolute ethanol.. This` solution was added to asolution prepared by dissolving one half mole of anhydrous magnesiumchloride in 200 cc. absolute ethanol. ing mixture was treated with anexcess of ammonium hydroxide, added slowly with agitation. The resultingprecipitate was separated and washed as usual.

Satisfactory catalysts can also be prepared by first forming activesilica and then uniting this with magnesia. Active silica suitable forthe purpose may be made by a wide selection of methods, some of whichwill be briey described.

Silica sol, silica hydrogel or silica gel can conveniently be made fromalkali metal silicates. Five hundred cc. of sodium silicate solutioncontaining l8,85% sodium oxide and 28.5% silicay are diluted with anequal volume of water. The thus diluted solution and 625 co. 6N sulfuricacid are simultaneously added, at rates proportional to their respectivevolumes, to a well agitated reaction vessel. A clear silica sol results.`This.

The result- `with the above directions usually has an inconexample, 6 to8 times. The washed hydrogelmay be dried to give silica gel.

vA somewhat more satisfactory active silica kfrom some points of viewcan be made by allowing the hydrogel to form at elevated temperatures,for example, 70 to 100 C. Since the time of set of acidied sodiumsilicate solutions decreases with extreme rapidity with increasingtemperature, a'reaction mixture prepared in accordance 10 venientlyshort time of set at high temperatures. This time of set can belengthened by using less acid than specified above, for example, 60 to'75% as much. Catalysts made from high temperature active silica aresomewhat more easily regenerated than those prepared from active silicamade at room temperature.

It is advisable to prepare active silica from acidiled sodium silicatesolutions but this is not absolutely essential. If desired, a sodiumsilicate solution may be brought almost but not quite to neutrality. Thealkaline hydrogel forms with extreme rapidity. This may be washed aspreviously described, using however slightly acidulated water in thefirst few washings. By this procedure a rapid time of set is obtainedwith the expenditure of a minimum amount of total acid.

Active silica prepared as above may be dried by a variety of methods.For example, the silica sol may be pumped through an atomizer into aheated room or heated gas stream to form silica gel in an extremely finestate of subdivision, the particles then being washed salt free. Thesame type of product may be made by injecting the sol into boilingliquid immiscible with Water, for example, boiling kerosene. When thesedrying methods are employed it is advantageous to use a volatile acid,for example, hydrochloric or acetic, in making the sol. Hydrogels,preferably after washing, may be dried by adding to a boil-N ing liquidimmiscible with` water, `f or-fexample boiling kerosene. Extremely fineactive ,silica particles result. If desired, washed hydrogel maybespreadout on trays and dried in an oven as usual. Thisvprol duces veryiine active silica although .tlviejnar-A ticle size is larger thanobtained when lth esses described immediately above: ar .l Y Frequently,silica gel particles of appreciablelgsize are desired. Such a productmay be'. cbt- Ved in" 50 several ways. For example, the wash gel, whenmechanically worked, knits gether again into a thixotropic gel.Thismay-- f be poured onto trays and dried in an oven? to-- give largeparticles, especially if the drying proceeds'slowly at rather lowtemperature. Or, the silica sol may be poured vonto trays to form layersabout one inch thick. When the sol has set, the hydrogel ispartiallydried' at a rather low temperature (say `150 F.) in a rapid stream ofair. By the time the water content has` reached to 60% salts begin toeiiioresce from thefpartially dried hydrogel particles which farexnow vabout A inch thick and one inch across.4 Drying is stopped and theparticles are covered with water and allowed to stand for say 30 minutesfollowing which the water is removed and replaced with fresh. Thisoperation is repeated several times, for example, 6 or 8 times. Thewashed, partially dried hydrogel particles are now completely dried togive a silicagel, practically all of which is retained on an 8 meshscreen. r

Active silica can also be made from ethyl orthosilicate. Seven hundredand fty ce. of ethyl orthosilicate ar diluted with 437.5 cc. ethanolfollowing which 14 `cc. of water are added. After standing 24 hours,127.5 cc. additional water are added and the resulting reaction mixtureis evaporated slowly to give pure silica gel.

A satisfactory active silica can also be made by slowly adding, withagitation, ammonium hydroxide to silicon tetrachloride, preferablydiluted with some solvent such as ethanol. The precipitate is washed anddried as usual.

Active silica, prepared as above or otherwise, may be united withmagnesia by. any` one of a variety ofmethods, some of which will now bebriefly described.

Example 8 Example 9 s Washed silica hydrogel (from sodium silicate) iscovered with a 10M solution of Mg(NO3) 26H2O and the mixture is allowedto stand several hours, preferably over night. Excess solution isremoved by draining and the impregnated hydrogel is dried ata relativelylow temperature F.) After drying, the temperature is raised to decomposethe nitrate.

Example 10 Six hundred andv fifty grams (dry basis) of washed silicahydrogel and 500g. (dry basis) of freshly precipitated, undried washedmagnesium hydroxide are mixed and worked mechanically to form ahomogeneous, somewhat thixotropic'gel.

" This is poured onto traysjand slowly dried at low temperature.

bile 1,1

, To a very slightiyaeidgsiiica hyarosol (containing 650 g; silica on.the .dry basis) are added 500 g. (dry basis) of freshly'pr'ecipitated,undried magnesium' hydroxide. uspension is stirred and 4ion atthe..boiling point rahours The resulting beingcontinued for;

,product is removedby vfiltration, vwashed and Vdried.

q' ge1 are mixed with-30o `g. (dry basis) of freshly precipitated,washed but4 undried magnesium hydroxide. The mixture is mechanicallyhomogenized, is extruded, cut to length and dried.

Y Example 13 4Example 14 v Three hundred and fifty g. of dry, activemagnesia and 650 g. of finely divided silica gel are mixed together in aball mill for several hours.

The resulting mixture is pelleted to form the final catalyst.

Example `superficial lil-metallic couple on the individual metalparticles using an element far from magneslum in the E. M. F. series.for example, mercury. Certain proprietary silica-magnesio. complexes eare also suitable contact agents for the purposes `of the instantinvention. Among these may be named: A

Example 16 This silica-magnesia` complex has been described in mycopending application, S. N. 300,390,

flied October 20, 1939 now U. S. Patent 2,278,590, issued April 7, 1942.

Ez'ample 17 I'his silica-magnesia complexhas been described in mycopending application, S. N. 398,242, filed June 16, 1941.

Example 18 P This silica-magnesia complex is prepared by Thissilica-magnesia complex is the mineral known ascoenite found, forexample, at Clay City. Nye County, Nevada some nine miles north of DeathValley Junction, California. This mineral contains (dry basis, ex. CO2)about 60% S102, 10% A1201 and 20% MgO and is quite efficient as acatalyst for the purposes of this invention, especially after a lightacid treat.

Example zo This silica-magnesia complex is .the mineral known as eyerltefound, for example, near Hector, California. This mineral contains (drybasis, ex. CO1) about 35% S102, 30% CaO and 15% MgO. It is fairlyemcient as a-contact agent for the purposes of this invention,especially after a light acid treat. A much more efficient catalyst canbe made by the hydrothermal reaction of finely ground eyerlte with asolution of a magnesium salt, for example, magnesium chloride. In thistreatment most of the lime is isomorphically replaced by magnesia. Ifdesired, the mineral may be lightly acid treated either before or afteror both before and after the hydrothermal reaction.

Satisfactorycontact agents for the purposes of the instant invention maybe made by rather drastically modifying certain natural materials.Illustrative of these methods, the following may be mentioned:

Example 21 This silica-magnesia complex is the material described inExample 3 of my copending application, s. N. 317,770. med February 7,1940, now U. s. Patent 2,320,799, issued June 1, 1943.

Example 22 An argillaceous material of the montmorillonitic orbentonitic type in iinely divided condition is subjected to hydrothermalreaction with a solution of a magnesium compound, for example, magnesiumchloride. The resulting product is separated by filtration, washed anddried. The speed of the hydrothermal reaction may be greatly increasedby conducting the reaction at superatmospheric pressure in an autoclave.

Example 23 An argillaceous material of the montmorillonitlc orbentonitic type is drastically overtreated with acid whereby al1 orpractically all of the activity as a cracking catalyst is lost. Sixhundred and fifty g. (dry basis) of the`resulting material is thoroughlymixed with 500 g. (dry basis) freshly precipitated, washed but undriedmagnesium hydroxide. The resulting mixture is then dried.

If desired, the silica-magnesia contact agents of. the instant inventionmay be activated or treated with activators prior to use. The catalystsmay be improved to a greater or less degree by giving them a lighttreatment at elevated temperatures with a dilute acid auch as` sulfuricacid or hydrochloric acid. Or, a small amount, for' example 5% byweight, of hydrofluoric acid may be added to the catalyst and theresulting mixture gently calcined. These treatments seem to loosen thestructure by removing a little magnesia and silica respectively. Ifdesired, both treatments may be applied to a single catalyst.

Certain'beneilclal results follow the addition of selected activators inrelatively small amounts to the catalysts of the instant invention.These `activators may be added during the preparation of the catalystsor the finished catalysts may be impregnated with thermally decomposablesalts of the activators following which the impregnated catalysts arecalcined. Among activators found to be more or less beneficial may bementioned boric oxide, beryllia, thoria, zirconia and alumina. About 5%or less of these activators, based on thev weight of the catalyst, maybeused..

Having now described by illustrative examples a representative selectionof silica-magnesia catalysts suitable for the purposes of the instantinvention, attention will be directed to a description of someillustrative process flows, employing the silica-magnesia catalysts ofthe instant invention, whereby the objects of the present invention areaccomplished. For the better understanding of the instant invention,attention is directed to the accompanying sheets of drawings forming apart of this application and wherein Figures 1 to 10 each comprise-adiagrammatic representation of a process ow whereby the objects of thepresent invention are accomplished.

It will be noted that each one of the figures is in flow sheet form,such essential but conventional pieces of equipment as Dumps, pipe stillfurnaces, reaction vessels, evaporators, ash and fractionating towers,heat exchangers, lines, valves, etcetera are for the most part notindicated. Also, the several possible methods for utilizing catalysts,for-example, by means of fixed bed catalytic reactors, moving bedcatalytic reactors, suspended catalytic reactors and the like are notshown. Additionally, there is no indicaomgen, more or less.

tion of the means employed to regenerate the catalysts periodically, forexample, by burning carbon and/or carbonaceous residues from the activesurfaces thereof. All of these details and manyothers are by nowfamiliar to those skilled Example 24 Turning now to a more detailedconsideration of Figure 1, a suitable hydrocarbon charge, for example,virgin gas oil, viscosity breaker gas oil, coker gas oil, reduced crudeor the like, is subjected to partial oxidation. 'lhe resulting reactionproducts are separated', eliminating preferably the lgas and waterformed during the oxidation, together with, if desired, any materialwithin the usual motor fuel range of boiling point. It is alsopreferable to eliminate as bottoms' any small amount of tar likematerial that may have formed during the oxidation. The resultingpartially oxidized liquid hydrocarbons, preferably of approximately thesame boiling range as the hydrocarbon charge, are passed to thecatalytic cracking zone wherein they are .contacted with asilica-magnesia catalyst, similar, for example, to that described inExample 1. The resulting products are separated into gas, Water,gasoline and cycle stock. If desired, cycle stock may be sent to storagethrough valve I, valve 2 being closed, or it may be recycled to thepartial oxidation-zone through valve 2, valve I being closed.

The exact process of partial oxidation employed .forms no part of-theinstant invention per se.

Any one of the many processes described in the prior art may b'eemployed. Briey, one suitable method for accomplishing this partialoxidation comprises vaporizing a hydrocarbon fraction and passing thevapors at 450 to 750 F., more or less, to a reactor wherein they arecontacted with 300 to 600 volumes of air (measureda's gas at standardconditions) per liquid volume of oil the reactor. Temperature was soregulated that thermocouples immersed Iin wells embedded in the pumicemounted catalyst registered an average temperature of approximately 700F. The

reaction products were cooled and separated, the gas passing overheadfrom the separator being scrubbed in an absorber with a portion of thehydrocarbon liquid bottoms from the separator,

charged. The air is preferably Vadded portionwise at a plurality ofpoints along the reaction vessel which may contain an oxidizing catalystif desired, such as vanadium oxide on purnice. The resulting productsare worked up`as usual and water (containing certain Water solubleoxidation products) is separated from the partially oxidized liquidhydrocarbons, the resulting partially oxidized liquid hydrocarbonscontaining from 3 to 8% When a relatively high boiling hydrocarbonfraction (such as a heavy gas oil or 4a reduced crude) is to beoxidized, vaporization may be aided with steam, recycle gas from theunit, or even a portion of the air to be used in the subsequentoxidation step.

More specifically illustrative of such an oxidation process is thefollowing: A light virgin gas oil boiling in the range 375 to 650 F. wasvaporized and passed at about 680 F. to the oxidizing re-4 actor at arate of 1.75 volumes liquid oil per hour per volume of reactionspace.The reaction space was filled with pumice carrying vanadium oxidethereon. Just at the entrance of the oxidizer, air was added to thevaporized charge at a rate of 125 volumes of air (measured as a gas atstandard conditions) per liquid volume of oil. Three additionalinjections of air, each in the volume previously stated were made, oneat one quarter through the reactor, one at the midpoint of the reactorand one at three quarters'through cracking zone.

the resulting rich absorber oil being mixed with the remainder of thesebottoms. Water was separated from the partially oxidized liquidhydrocarbons and the latter were fractionated, taking overhead about 15%material falling in the gasolineboiling range and eliminating a trace oibottoms as tar.

The partially oxidized liquid hydrocarbons, formed as above described(after removal of material in the motor fuel boiling range and afterremoving thev small amount ofV tar like material that was present), werebrought to a temperature of 975 F. and passed over the silica magnesiacatalyst of Example 1 at a rate of 2.25 liquid vlumes per hour pervolume of reactor space. The gasoline yield was about 30%.

A separate portion of the partially oxidized liquid hydrocarbon chargingstock prepared as above described was heated to 1000 F. and passed overthe catalyst of Example 17 at a rate of 3.0 liquid volumes per hour pervolume of catalyst reactor space. The resulting product contained 25% byvolume of gasoline of 80 octane number.

Supplementary experiments were run in which cycle stock from thecatalytic cracking of partially oxidized liquid hydrocarbons wasrecycled to the partial oxidation zone. By lthis procedure a fairly highultimate yield of gasoline was obtained. I

- It'will be obvious immediately that the above described processv is ofrather limited utility.

Since virgin stocks as Well as non-refractory processed stocks such asviscosity breaker gas oils Y Example 25 Referring to Figure 2, asuitable hydrocarboncharge, for. example, virgin gas oil, viscositybreaker gas oil, coker gas oil, reduced crudeor the like iscatalytically cracked in a first catalytic rated into gas, gasoline andcycle stock, the latter being subjected to partial oxidation essentiallyas described in Example 24, or otherwise, as desired.

'I'he partially oxidized liquid hydrocarbons are vaporized and passedthrough a second catalytic cracking zone containing a silica-magnesiacata.

lyst, similar, for example, to that described in Example 17. Theproducts are separatedinto gas, water, gasoline and cycle stock. Thislast may be sent to storage through valve I, valve 2 being closed, or itmay be recycled to the partial in the example to The resulting productsare sepa.

resulting from processing the cycle stock from the 1li-st catalyticcracking zone, gave a once through gasolineyield of 26% whencatalytically cracked in the second catalytic cracking zone at 1000 F.`

at a flow rate of 2.25 liquid volumes of charge per hour per volume ofcatalytic reactor space, the previously mentioned silica-magnesia4contact agent being employed. By recycling cycle stock from this secondcatalytic cracking zone to the partial oxidation zone a high ultimateyield of gasoline is attained.

The nature of the contact agent in the first catalytic cracking zone islargely a matter of choice although certain rules in its selection arepreferably to be followed. If the hydrocarbon charge is not refractoryand is one of comparatively iow boiling point, for example, with an A.S. T. M. endpoint of 750 F. or less, as exemplied by light virgin gasoil, light viscosity breaker gas oil or light coker gas oil then,preferably, a catalyst from class'II is employed, for example, asynthetic silica-alumina catalyst of the prior art, many of which havebeen described in certain `of my copending applications such as S. N.277,580, iiled June 6, 1939 nowU. S. Patent 2,353,624, issued July 11,V1944; S. N. 277.885, filed June 7, 1939;

S. N. 305,472, led November 21, 1939; S. N. 305,-

473, filed November 21, 1939; S. N. 313,898, led January 15, 1940 now U.S. Patent 2,323,798, issued July 6, 1943; S. N. 317,770, filed February7, 1940 now U. S. Patent 2,320,799, issued June 1, 1943; S. N. 321,651,filed March 1, 1940; S. N. 334,741, led May 13, 1940 now U. S. Patent2,312,445, issued March 2, 1943; and S. N. 346,809, led July 22, 1940now U. S. Patent 2,366,217, ls.- sued January 2 1945. When a highlyactive synthetic silica-alumina catalyst is` employed,

satisfactory conversions of non-refractory, easily lvaporized chargingstocks to gasoline are obtained at relatively low catalytic crackingtemperatures and relatively high throughputs. A relatively lowvtemperature is all that is necessary to achieve complete vaporization ofsuch stocks so it is accordingly distinctly advantageous to use acatalyst exhibiting satisfactory activity at such a relatively lowtemperature. Catalysts of class I, as exemplied by Super Filtrol andTonsil (both being trade names applied to acid treated argillaceousmaterials of a montmorillonitic or bentonitic type) may be employed buthere the low activity is preferably overcome in part by eitherincreasing the cracking temperature or decreasing throughput or both,preferably by decreasing the `flow rate, since at relatively highcatalytic crackingtemperatures class I catalysts give poor productdistributions, that is, a low ratioof desired conversion product toundesired conversion products. Also, class III catalysts, severalexamples of which have already been given, may be ernployed, but hereagain low activity is preferably overcome as mentioned above. Class IIIcatalysts however have an advantage over class I catalysts in that theformer usually give a better product distribution at relatively highcatalytic cracking temperatures.

If, on the other hand, a non-refractory, comparatively high boilinghydrocarbon charge is employed, such as heavy virgin gas oil, reducedcrude, heavy viscosity breaker gas oil or a heavy coker oil, arelatively high temperature is required for vaporization. If the highlyheated vapors are passed over a class II catalystyconsiderable over- Jcracking occurs, giving a poor product distribu- ,tion which may howeverbeovercome to a certain extent by increasing the throughput. Class Icatalysts are more satisfactory but they exhibit previously mentioneddisadvantages. Class III catalysts. several of which have been mentionedin' previous examples, are about ideal since they give a good productdistribution and exhibit satisfactory activity at high temperatures.Furthermore, with class III4 catalysts, steam may be employed to aid invaporization of the heavy stock Without affecting 'catalytic activity.

When refractory cycle stocks are charged, for

, example, cycle stocks from either thermal or range of the charge.

catalytic cracking processes, a class II catalyst is preferablyemployed, regardless of the boiling Due-to the refractory nature of thecharge, a high temperature and a highly active catalyst must be used toachieve relatively high conversions. Class III catalysts may be used butare less satisfactory due to their lower activity but if the charge isso high boiling that steam as a vaporization aid is almost essentialthen class III catalysts are preferable to class II catalysts.

To summarize the above the following table is presented: l

Charging stock Preferred catalyst I. Nouwen-notary:

A. Low boiling Class II. B. High boiling Glass III. Il. Refractory:

A. Low boiling Class II. B. High boiling Class II or III.

Example 26 y' A light, non-refractory gas oil, for example, a lightvirgin gas oil, a light viscosity breaker ga`s oil or a light coker gasoil is contacted pref-- erably with a synthetic silica-alumina catalystat a relatively low catalytic cracking temperature as shown in Figure 3.Cycle stock from this operation is mixed, if desired, with a heavy gasoil of a non-refractory nature for example, a heavy virgin gas oil, aheavy viscosity breaker gas oil or a heavy coker gas oil introducedthrough valve 3, and the blend is contacted preferably with asilica-magnesia catalyst, for example, the contact agent of Example 10,at a relatively high catalytic cracking temperature in a secondcatalytic cracking zone. Cycle stock from this operation is partiallyoxidized as before described or otherwise and the resulting partiallyoxidized liquid hydrocarbons are contactedpreferably with. asilica-magnesio. catalyst, for example, the contact agent of Example 10,at a relatively high catalytic cracking temperature in a third-catalyticcracking zone. Cycle stock from this operation may be sent to storagethrough valve I, valve 2 being closed, or it may be recycled to thepartial oxidation zone through valve 2, valve l Vbeing closed.

Emample 27 In Figure 4, light, non-refractory gas oil of the naturepreviously described, is contacted preferably'with a syntheticsilica-alumina catalyst at a relatively low catalytic crackingtemperature while heavy, non-refractory gas oil of the nature previouslydescribed is separately contacted, preferably with a silica-magnesiacatalyst, for example, that of Example 18, at a relatively highcatalytic cracking temperature. Cycle stocks from these two operationsare mixed and the resulting blend is partially oxidized as previouslydescribed or otherwise and theresulting partially v oxidized liquidhydrocarbonsare contacted in a third catalytic cracking zone with asilica-magnesia catalyst, for example, that of Example 18, preferably ata relatively highcatalytic cracking temperature. Cycle stockfrom thisoperation may be sent to storage if desired through valve I, valve 2being closed, or maybe recycled to the partial oxidation zone throughvalve 2, valve I being closed. Example 28 In Figure 5, light,non-refractory gas oil of the nature previously described is contactedpreferably with a synthetic silica-alumina catalyst at a relatively lowcatalytic cracking temperature. Heavy, non-refractory gas oil of thenature previously described is separately contacted, preferably with asilica-magnesia catalyst, vfor ex-l ample, that of Example l, .at a,relatively high catalytic cracking temperature. Cycle v'stocks fromthese two operations are mixed andtheresulting blend is contactedpreferably with a synthetic'silica-alumina catalyst at a relatively highcatalyticv cracking temperature in a third catalytic cracking zone,lwhereby a v'substantial Aoi the nature previously described iscatalytically cracked, preferably at a relatively low catalyticconversion of this refractory charge -is achieved.

Cycle stock from this third catalytic cracking zone V'is partiallyoxidized as previously described or-v otherwise and the resulting"partially .oxidized liquid hydrocarbons are contacted., in a fourthcatalytic cracking zone, -with a silica-magnesia catalyst, for example,that of Example 3, preferably at a relatively high catalytic crackingtemperature. Cycle stock from this operation may be sent to storagethrough `valve I, valve 2 being closed, orl may be recycled to thepartial oxidation zone through valve 2, valve I being closed. In severalexamples4 to follow, process 'flows' that require less equipment but onthe other hand are less flexible than those shown in Figures 1 to 5 aredescribed.

Example 2li A non-refractory hydrocarbon charge of the nature previouslydescribed, in admixture with a material subsequently to be specified, iscatalyticaily cracked over a silica-magnesia catalyst, for example, thatof Example 16,'preferably. at a catalytic cracking temperature. Cyclestock from l this second catalytic cracking zone is partially oxidizedas previously described or otherwise and the resulting partiallyoxidized liquid hydrocarbons are mixed with cycle stock from the ilrstmentioned catalytic cracking zone, the blend ,being passed to the secondcatalytic cracking zone.

Eample 31 In Figurel 8, a light, non-refractory gas oil of the naturepreviously described is catalytically cracked, preferably at arelatively low catalytic cracking temperature with a silica-aluminacatalyst. A heavy, non-refractory gas oil of the na- "ture previouslydescribed in admixture with a 'material subsequently to be specied ischarged to a second catalytic cracking zone employing a silica-magnesiacatalyst, for example, that of Example 9, and preferably operating at arelatively high catalytic cracking temperature. Cycle stock from bothcatalytic cracking zonesis blended and the lmixture is partiallyoxidized as previously described or otherwise, the resulting partiallyoxidized liquid hydrocarbons being admixed with the aforementioned heavygas oil followingwhich the blend` is passed to the second catalyticcracking zone.

n Ezample-32 ...In lFigure 9, a light, non-refractory gas oil ofcracking temperature in the presence of a silicaalumina catalyst. Heavynon-refractory gas oil ofthe nature .previously described, in admixturewith -a material subsequently to be specified, is processed in a secondcatalytic cracking zone in contact with a silica-magnesia catalyst, forexample, that of Example 2, and preferably at a relatively highcatalytic cracking temperature. Cycle stocks from both catalyticcracking zones are blended and the resulting mixture is passed to athird catalytic cracking. zone operating at relatively high catalyticcracking temperature.l

Cycle stock from this operation is partially ox- `idized as previouslydescribed or otherwise and the resulting partially oxidized` liquidhydrocarbons are mixed with thepreviously mentioned a high catalyticcracking temperature relatively and employing a silica-,aluminacatalyst. Cycle stock from this third catalytic cracking zone ispartially oxidized as previously described or otherwise and theresulting partially oxidized liquid hydrocarbons areadmixed with theheavy gas oil prior to passage .to the second catalytic cracking zonepreviously mentioned.

Example 33 f Q/ In Figure 10, a light, non-refractory gas oil ofthe-nature previously described is catalytically cracked, preferably ata relatively low catalytic cracking temperature in the presence of asilicahydrocarbon-'charge to the' catalytic cracking zone and theresultingblend is passed thereto. See Figure 6.

In Figure 7,.a light noun-refractory.gasv oil ofl the nature previouslydescribed is catalytically cracked, preferably at av relatively lowcatalytic alumina catalyst. Heavy, non-refractory gas oil of the naturepreviously described, is processed 'in a vsecond catalytic cracking`zone preferably I. at a 4relatively high catalytic crackingtemperaturein contact with a silica-magnesia cracking catalyst, forexample, that of Example 1. Cycle ,stock from both catalytic crackingzones is blended and in admixture with al material subsequently to bespecified is processed in a third catalytic cracking zone in contactwith a silicamagnesia catalyst, for example, that of Example :1,preferably at a relatively high catalytic crackcopending application, S.N. 398,242, led June While the instant invention has been describedlargely through the medium of certain specific examples' thereof, it isto be understood that these examples 4are illustrative only and are inno way to be construed as limitations upon the l spirit and scope of theinvention.

I claim:

l. A method of converting hydrocarbons of higher boiling point intohydrocarbons of lower boiling point comprising' admixing saidhydrocarbons of higher boiling point with air, maintaining the resultingmixture at an oxidizing temperature for a time suiiicient to effectsubstantial partial oxidation of said hydrocarbons of higher boilingpoint, separating the resulting partially oxidized liquid hydrocarbonsfrom materials boiling within and below the usual motor fuel range andcontacting said partially oxidized liquid hydrocarbons with asilica-magnesia cracking catalyst at a cracking temperature for a timesufficient to effect substantial conversion of said partially oxidizedliquid hydrocarbons to hydrocarbons of lower boiling point.

2. The method of claim l, further characterized by the fact that cyclestock is separated from the products resulting from the catalyticcracking of said partially oxidized liquid hydrocarbons and is recycledto the partial oxidation zone.

3. A method of converting hydrocarbons of higher boiling point intohydrocarbons of lower boiling point comprising contacting saidhydrocarbons of higher boiling point with a cracking catalyst at acracking temperature for a time sufficient to eiect substantialconversion of said hydrocarbons of higher boiling point intohydrocarbons of lower boiling point, separating the resulting productsinto gas, gasoline and cycle stock,admixing said cycle stock with air,maintaining the resulting mixture at an oxidizing temperature for a timesufficient to eiiect substantial partial oxidation of said cycle stock,separating the resulting partially oxidized cycle stock from materialsboiling within and below the usual motor fuel range and contacting saidpartially oxidized cycle stock with a silica-magnesia cracking catalystat a cracking temperature for a time suilicient to eiect substantialconversion of said partially oxidized cycle stock to hydro.- y

fect substantial conversion of said charge to hydrocarbons of lowerboiling point, separating the resulting products `into gas, gasoline andcycle stock, contacting said cycle stock with a cracking catalyst in asecond catalytic cracking zone at a cracking temperature for a timesuiiicient to effect substantial conversion o1' said charge tohydrocarbons of lower boiling point, separating the resulting productsinto gas, gasoline and cycle stock, admixing the cycle stock from saidsecond catalytic cracking zone with air, maintaining the resultingmixture at an oxidizing temperature for a time suiiicient to eectsubstantial partial oxidation of said last-named cycle stock, separatingthe resulting partially oxidized cycle stock from materials boilingwithin. and below the usual motor fuel range and contacting saidpartiallyA oxidized cycle stock with a silica-magnesia cracking catalystin a third catalytic cracking zone at a cracking temperature for la timesuillcient to effectsubstantial conversion of said partially oxidizedcycle stock to hydrocarbons of lower boiling point.

6.'The method of claim 5, further characterized by the fact that cyclestock is separated from the products resulting from the catalyticcracking o1 said partially oxidized cycle stock and isl recycled to thepartial oxidation zone.

7. The method of claim 5, further characterized by the fact that saidhydrocarbons of higher boiling point are of the nature of light gasoil.

8. The method of claim 5, further characterized by the fact that saidhydrocarbons of higher boiling point are of the nature of light gas oiland that cycle stock is separated from the products resulting from thecatalytic cracking of said partially oxidized cycle stock and isrecycled to the partial oxidation zone.

9. The method of claim 5, further characterized bythe fact that saidhydrocarbons of higher boiling point are of the nature of heavy gas oil.

l0. The method of claim `5, further characterized by the fact that saidhydrocarbons oi' higher boiling point are of the nature of heavy gas oiland that cycle stock is separated from the products resulting from thecatalytic cracking of said partially oxidized cycle stock and isrecycled to the partial oxidation zone.

11. A method of converting hydrocarbons of Vhigher boiling point intohydrocarbons of lower boiling point comprising contacting a firsthydrocarbon fraction 0i higher boiling point with a cracking catalyst ina iirst catalytic cracking zone at a cracking temperature for a, time.suflcient to eiect substantial conversion of said charge tohydrocarbons of lower boiling point, separating the resulting productsinto gas, gasoline and cycle stock, admixing a second hydrocarbonfraction of higher boiling point which is of substantially differentboiling range from that of said rst hydrocarbon fraction with said cyclestock, contacting the resulting blend,A with a cracking catalyst in asecond catalytic cracking zone at a cracking temperature for a timesuflicient to effect substantial conversion of said charge tohydrocarbons of lower boiling point. separating the resulting productsinto gas, gasoline and cycle stock, admixing the cycle stock from saidsecond catalytic cracking zone with air, maintaining the resultingmixture at an oxidizing temperature for a time'suilicient to eiectsubstantial partial oxidation of said last-named cycle stock, separatingthe resulting partially oxidized cycle stock from materials boilingwithin and below the usual motor fuel range and contacting saidpartially oxidized stock with/a silicamagnesiol cracking catalyst in athird catalytic cracking zone at a cracking temperature for a timesuiiicient to effect substantial conversion of said partially oxidizedcycle stock to hydrocarbons of lower 'boiling point.

12. The method of claim 1i, further characterized by the fact that athird cycle stock is separated from the products resulting from thecatalytic cracking of VVsaid partially oxidized cycle stock and isrecycled to the partial oxidation zone.

13. 'I'he method of claim 1l, further characterized by the fact thatsaid ilrst hydrocarbon fraction is of the nature of light -gas oil andsaid second hydrocarbon fraction is of the nature of heavy gas oil.

14. The method, of claim 11, further characterstock blend and isrecycled to the partial oxidation zone. 19.7A method of convertinghydrocarbons of v ized by the fact that said first hydrocarbon 'frac- Ytion is of the nature of light gas oil and said heavy gas oil and that athird cycle stock is separated from the products resulting from thecatalytic cracking of said partially oxidized cycle stock and isrecycled to the partial oxidation zone.

15. The method of claim 1l, further characterized by the fact that saidrst hydrocarbon fraction is of the` nature of heavy gas oil and saidsecond hydrocarbon fraction is of the nature of light gas oil.

16. The method of claim 11,`further characterized by the fact that saidrst hydrocarbon fraction is of the nature of heavy gas oil and saidsecond hydrocarbon fraction is of the nature of light gas oil and that athird cycle stock is separated frorn'the products resulting from thecatalytic cracking of said partially oxidized cycle stock and isrecycled to the partial oxidation zone. f

17. A method of converting hydrocarbons of higher boiling point intohydrocarbons oflower boiling point, comprising contacting a hydrocarbonfraction of the nature of light gas oil with a cracking catalyst in a.first catalytic cracking zone at a cracking temperature for a timesumcient to eifect substantial conversion of said charge to hydrocarbonsof lower'boiling point, separating the resulting products` into gas,gasoline and cycle stock; contactinga hydrocarbon fraction of the natureof heavy gas oil with a cracking catalyst in a, second catalyticcracking zone at a cracking temperature for a time sufcient to effectsubstantial conversion of said charge to hydrocarbons of lower boilingpoint, separating the resulting products into gas, gaso-` line and cyclestock; combining the cycle stocks from said rst and second catalyticcracking zones, admixing the resulting blend with air and maintainingthe resulting mixture at an oxidizing temperature for a time `sumcientto eiect substantial partial oxidation of said cycle stock blend,separating the resulting partially oxidized cycle stock blend frommaterials boiling within and below the usual motor fuel range andcontacting said partially oxidized cycle stock blend with asilica-magnesia cracking catalyst in av third catalytic cracking zone ata cracking temperature for a time sufllcient to effect substantialconversion of said partially oxidized cycle stock blend to hydrocarbonsof lower boiling point.

18. Themethod of claim 17, further characterized by the fact that athird cycle stock is separated from the products resulting from thecatalytic. cracking of said partially oxidized cycle higher boilingpoint into hydrocarbons of lower boiling point, comprising contacting ahydrocarbon fraction ofthe nature of light gas oil with a crackingcatalyst in a iirst catalytic cracking zone at a cracking temperaturefor a time suincient to eiect substantial conversion of said charge tohydrocarbons of lower boiling point, separating the resulting productsinto gas, gasoline and cycle stock; contacting a hydrocarbon fraction ofthe nature of` heavy gas oil with a cracking catalyst in a secondcatalytic cracking zone at a cracking temperature for a time sulficientto effect substantial conversion of said charge to hydrocarbons of lowerboiling point, separating the resulting products into gas, gasoline andcycle stock; combining the cycle stocksy from said first and secondcatalytic cracking..

cient to eect substantial conversion of said blend to hydrocarbons oflower boiling point, separating the resulting products into gas,gasoline and a third cycle stock, admixing said third cycle stock withair and maintaining the resulting mixture at an oxidizing temperaturefor a time sufficient to eiect substantial partial oxi-. dation of saidcycle stock, separating the resulting partially oxidized cycle stockfrom materials boiling within and below the usual motor fuel range andcontacting `said partially oxidized cycle stock with a silica-magnesiacracking catalyst in a fourth catalytic cracking zone at a crackingtemperature for a time suillcient to effect substantial conversion of.said partially oxidized cycle stock to hydrocarbons of lower boilingpoint.

20. 'I'he method of claim 19, further characterized by the fact that afourth cycle stock is separated from the products resulting from thecatalytic cracking of said partially oxidized cycle stock and isrecycled to the partial oxidation zone. 2l. A method of convertinghydrocarbons of higher boiling point into hydrocarbons of lower boilingpoint comprising contacting said hydrocarbons of higher boiling point,in admixture with a partially oxidized cycle stock subsequently to bedescribed, with a silica-magnesia cracking catalyst at a crackingtemperature for a time suf'- cient to effect substantial conversion of.the charge into hydrocarbons of lower boiling point,

separating the resulting products into gas, gasoboiling point comprisingcontacting a hydrocar-` bon fraction of higher boiling point with acracking catalyst in a rst catalytic cracking zone at a crackingtemperature for a time suilicient to effect substantial conversion ofsaid charge t0.

hydrocarbons of lower boiling point, separating 'the resulting productsintogas, gasoline and cycle stock, contacting said cycle stock, inadmixture with a partially oxidized cycle stock subsequently to bedescribed, with a silica-magnesia cracking assauts. 1 1

`catalyst in a second catalytic cracking zone at a cracking temperaturefor a time suiflcient to effect substantial conversion of the chargeinto hydrocarbons of lower boiling point, separating the resultingproducts into gas, gasoline, water and a second cycle stock, admixingsaid second cycle stock with air, maintaining the resulting mixture atan oxidizing temperature for a time vsuilicient to eiiect substantialpartialv oxidation light gas oil.

24. The method of claim 22 further characterized by the fact that saidhydrocarbon frac- .tion of higher boiling point is ofthe nature of heavygas oil.

25. A method of converting hydrocarbons of higher boiling point intohydrocarbons of lower boiling point comprising contacting a firsthydrocarbon fraction of higher boiling point with a cracking catalyst ina first catalytic cracking zone at a cracking temperature for a timesutilcient to eilect substantial conversion of said charge tohydrocarbons of lower boiling point, separating the resulting productsinto gas, gasoline and cycle stock, admixing 'a second hydrocarbonfraction of higher boiling point and which is of substantially diilerentboiling range than that cf said first hydrocarbon fraction with saidcycle stock, contacting the resulting blend in admixture with apartially oxidized cycle stock y subsequently to be described, Withasilica-magnesia cracking catalyst in a second catalytic cracking zone ata cracking temperature for a time suiiicient to eilect substantialconversion of the charge into hydrocarbons of lower boiling point,separating the `resulting products into gas, gasoline, water and asecond cycle stock, admixing said second cycle stock with air,maintaining the resulting mixture at an oxidizing temperature for a timesuiiicient to effect substantial partial oxidation of said second cyclestock, separating the resulting partially oxidized cycle stock frommaterials boiling within and below the usual motor fuel range and addingsaid par- .tially oxidized cycle stock to the charge to said secondcatalytic cracking zone.

26V. The method of claim 25, further characterized by the fact thatsaidiirst hydrocarbon fraction is of the nature of light gas oil and saidsecond hydrocarbon fraction is of the nature of heavy gas oil.

27. The method of claim 25, further charac-4 terized by the fact thatsaid iirst hydrocarbon fraction is of the nature of heavy gas oil andsaid second hydrocarbon fraction is of the nature of light gas oil.

28. A method of converting hydrocarbons of higher boiling point intohydrocarbons of lower boiling point comprising contacting a firsthydrocarbon fraction of higher boiling point with a cracking catalyst ina first catalytic cracking zone at a cracking temperature for a timesufiiient to effect substantial conversion of said charge tohydrocarbons of lower boiling point,

is of substantially different boiling range than that of said firsthydrocarbon fraction, in Aadmixture with a partially oxidized cyclestock subsequently to be described, with a silica-magnesia crackingcatalyst in the second catalytic cracking zone at a cracking temperaturefor a time suicient to effect substantial conversion of said charge tohydrocarbons of lower boiling point,

separating the resulting products into gas, water,

gasoline and cycle stock; combining the cycle stocks from said rst andsecond catalytic cracking zones, admixing the resulting blendV with airand maintaining the resulting mixture at an oxidizingtemperature for atime sufficient to effect substantial partial oxidation of said cyclestock blend, 'separating the resulting partially oxidized cycle stockblend from materials boiling within and below the usual motor fuel rangeand adding said partially oxidized cycle stock blend to the charge tothe second catalytic cracking zone.

29. The 'method of claim 28, further characterized bythe fact that saidrst hydrocarbon frac-` tion is of the nature of light gas oil and saidsecond hydrocarbon fraction is of the nature of heavy gas oil.

30. The method of claim 28, further characterized by the fact that saidfirst hydrocarbon fraction is of the nature of heavy gas oil and saidsecond hydrocarbon fraction is of the nature of light gas oil.

31. A method of converting hydrocarbons of higher boiling point intohydrocarbons of lower boiling point comprising contacting a ilrsthydrocarbon fraction of-higher boiling point with a cracking catalyst ina rst catalytic cracking zone at acracking temperature for a vtimesutilcient to effect substantial conversion of said charge tohydrocarbons of lower boiling point,.

separating the resulting products into gas, gasoline and cycle stock;contacting a second hydrocarbon fraction of higher boiling point andwhich is of substantially different boiling range than that of saidfirst hydrocarbon fraction in admixture with a partially oxidized cyclestock subsequently to be described, with a silica-magnesia crackingcatalyst in a second catalytic cracking zone at a cracking temperaturefor a time sufficient to effect substantial conversion of' said chargeto hydrocarbons of lower boiling point, separating the resultingproducts into gas, water, gasoline and cycle stock; combining cycle.stocks from said first and second catalytic cracking zones, contactingthe resulting blend with a cracking catalyst in a third catalyticcracking zone at a cracking temperature for a time suiilcient to effectsubstantial conversion of said charge to hydrocarbons of lower boilingpoint, separating the resulting products into gas, gasoline and a thirdcycle stock, admixing said third cycle stock with air and maintainingthe resulting mixture at an oxidizing temperature for a time sufficientto effect substantial partial oxidation of said third cycle stock,separating the resulting partially oxidized cycle stock from materialsboiling Within andbelow the usual motor fuel rangeV and adding saidpartially oxidized cycle stock to the charge to said second catalyticcracking zone.

32. The method of claim 31, further characterized by the fact that said'rst hydrocarbon fraction is of the nature of light gas oil and saidsecond hydrocarbon fraction is of the nature of heavy gas oil.

33. The method of claim 31, further characterized by the fact that saidfirst hydrocarbon fraction is o! the nature oi.' heavy gas oil saidsecond hydrocarbon traction is of the nature 'of light )gas oil.

' 34. A method of converting hydrocarbons of higher boiling point intohydrocarbons ot lower boiling point comprising contacting a hydrocarbcnfraction o! the nature of light gas oil with a cracking catalyst in arst catalytic cracking A fraction ol the nature of h eavy gas oil withacracking catalyts in a second catalytic cracking zone at a crackingtemperature for a time sumcient to eilect substantial conversion of saidseparating the resulting products into gasrgasoline and cycle stock;combining cycle stocks from andl ' charge into hydrocarbons of lowerboiling point.

:anni

said nrst 4and second catalytic cracking zones.

contacting the resulting blend. in admixture with partially oxidizedcycle stock subsequently to be described, with a silica-magnesio.cracking catalyst in a third catalytic cracking zone at a crackingtemperature for a time suilicient to eiect substantial conversion cisaid charge to hydrocarbons of lower boiling point, separating theresulting products into gas, gasoline, water and a third cycle stock,admixing said third cycle stock with air and maintaining the resultingmixture at an oxidizing temperature for a time suillcient to eifectsubstantial partial oxidation of said third cycle stock, separating theresulting partially oxidized cycle stock from materials boiling within'and below the usual motor fuel range and adding said partially oxidizedcycle stock to the charge to said third catalytic cracking zone.

ROBERT F. RUTHRUFF.

